interesting.... If the gateway ecu was faulty and stopping the car from starting then the Ford ECU would list a fault code from memory ecu disabled or fuel pump/driver module off line. Also it should show engine disabled on the dash.
The gateway only links the ford ecu to the bmw ews so it can start the car and the ecu for an auto is different. The car need to go on a T4 and see what the codes listed are.

Is there any water in the boot or any of the carpets wet??